It is often desirable to use goggles or protective eye-shield masks for protecting one's vision from invasion of the eyes by snow, ice, precipitation or other elements such as airborne or wind-blown particles, and also to enable clear vision during participation in various activities such as outdoor winter sports, skiing, hiking, sledding, tubing, mountaineering, climbing, ice climbing, snowboarding, snowmobiling, paintballing, swimming, scuba diving, snorkeling, hazardous activities requiring safety eye protection, industrial use, target shooting, police work, tactical operations, riot control, corrections or military use. It is also often necessary to use such goggles or masks in environments involving conditions which contribute to condensation build-up on the eye-shield and where even momentary impairment of vision by fogging would be problematic. In such environments, when the temperature of such an eye-shield drops below a dew-point temperature, i.e., the atmospheric temperature below which water droplets begin to condense and dew can form, fogging occurs.
Thus, fogging that impairs vision is a common problem with such goggles and masks, and there have been various conductive apparatus devised for preventing condensation build-up on eye-shields for eye-protecting shields. The purpose of these conductive apparatus has been to provide an eye-shield that may be maintained free of condensation so that the user would be able to enjoy unobstructed vision during viewing activities. Prior goggles with electronic systems that have been primarily used in environments requiring a high degree of portability have included a thin-film heating element, such as Indium Tin Oxide (ITO) or other thin-film heating element, on a lens that is used in a goggle having a power source carried on the frame or strap of the goggle for powering the electronics for the goggle such as has been shown and described in co-pending U.S. patent application Ser. No. 61/563,738, by McCulloch, for Modular Anti-fog Goggle System.
There are currently two different types of commonly available goggle or protective eye-shield lens form factors for protecting one's vision from invasion of the eyes by snow, ice, precipitation or other elements such as airborne or wind-blown particles: those having a cylindrical eye-shield or lens, and those having a spherical, or toric, eye-shield or lens. The first type of commonly available goggles and protective eye-shield masks has a cylindrical eye-shield. Cylindrical eye-shields are common in goggles and eye-shield masks because they have been generally less expensive and easier to manufacture. This advantage in lower-cost manufacturing has come with at least a somewhat perceived cost to wearers of cylindrical eye-shields however. Some Cylindrical eye-shields have been claimed by some to impair, impede, or distort the vision of the wearer. Some Cylindrical eye-shields also have been claimed by some to create a limited viewing window for wearers, concentrating their field of vision to what is directly in front of them. Additionally, because of the flat surface of the cylindrical eye-shield, light enters the lens at different angles which is considered by some to distort the image that the wearer sees and to create glare. These disadvantages have created a potential for hazards. Cylindrical eye-shields have also recently been determined by the Applicant to have advantageous properties when used in connection with lens heating systems.
The second, currently more fashionable, appealing to the eye and desirable type of commonly available goggle has a spherical, or toric, eye-shield. Although spherical eye-shields have been somewhat more difficult and expensive to design and manufacture, they are currently considered more fashionable and desirable than cylindrical eye-shields because some have been reputed as providing wearers with better comfort, a higher quality image, and an overall more pleasing appearance and enjoyable experience. Some claim that because the surface of spherical eye-shields comprise curved convex outer surfaces and concave inner surfaces, they conform better to the natural curves of a human head, allowing the wearer a tighter and more uniform fit. Assuming an optical-grade quality level, spherical eye-shields are also said by some to allow light to pass through them in more of a straight line, creating a less distorted image than that of a cylindrical eye-shield. An additional benefit to spherical eye-shields is they may help to prevent glare, or are at least perceived as doing so by some, lessening the potential for hazards than may otherwise be the case with cylindrical eye-shields. Thus, spherical lens eye-shields have been more fashionable and desirable for wearers of goggles.
When applying ITO to eye-shields for use as a thin film-heating element, it is important to achieving even heating (at least given a uniform eye-shield surface area) that the ITO is applied uniformly across the surface of the eye-shield. Absent intentional design for irregular-shaped lenses as described in co-pending U.S. patent application Ser. No. 14/040,683, by Cornelius, for Multiregion Heated Eye Shield, an irregular coating of ITO on the surface will create an undesirable uneven resistance in the material and result in undesirable uneven heating. Applying a substantially even coat of ITO across the surface of a cylindrical eye-shield has been relatively simple and cost effective to design and manufacture, since the ITO has been applied by a film backing or ion sputtering to a flat surface lens, which has then later been shaped to form a cylindrical lens. Or alternatively, the ITO may have been deposited relatively easily on the inner cylindrical surface with a film backing or by ion sputtering, as the case may be. It is apparent therefore, that the relatively easier and cost effective process of applying ITO to a cylindrical lens has not allowed easy production of a heated lens that is also more desirable and spherical, or toric, in shape. Thus there has developed a need in the industry for a cost effective way to provide a thin-film heated lens for a goggle or eye-shield mask that is also spherical and currently fashionable and desirable.